1. Field of the Invention
The present invention relates to a planar light-source apparatus.
2. Description of the Related Art
In a liquid crystal display, a liquid crystal material itself does not emit light. Hence, a direct-lighting type planar light-source apparatus (backlight) is arranged on the back of a display area, composed of a plurality of pixels, of a liquid crystal display for illuminating the display area (see Nikkei Electronics No. 889, Dec. 20, 2004, p123 to 130). In a color liquid crystal display, one pixel is composed of a red-luminous sub-pixel, a green-luminous sub-pixel, and a blue-luminous sub-pixel. A liquid crystal cell constituting a pixel or a sub-pixel is operated as a kind of optical shutter (light valve) so as to control the light transmittance (open area ratio) of the pixel or the sub-pixel. Thereby, images are displayed by controlling the light transmittance of illuminating light (white light, for example) emitted from the planar light-source apparatus.
The planar light-source apparatus (backlight) includes a casing, a plurality of light sources arranged within the casing, and a diffusing plate arranged in an upper portion of the casing. The light source may include a light emitting diode (LED) and a cold cathode-ray fluorescent lamp. The diffusing plate is generally made of plastics, and has a thickness of about 2 mm, depending on the size of the liquid crystal display. Its rigidity is not enough for maintaining the flatness by itself when it is held horizontal. Hence, for supporting the plastic diffusing plate, a columnar or conical brace is arranged within the casing. The end extremity of the brace is not in contact with the diffusing plate normally; however, during manufacturing and transporting the planar light-source apparatus or during assembling the planar light-source apparatus with the liquid crystal display and transporting the assembly of both the apparatuses, the end extremity of the brace may come in contact with the diffusing plate, so that the damage of the diffusing plate can be prevented due to its deflection.